This invention relates to a connector, and relates more particularly but not exclusively to a connector for connecting coiled tubing to a Bottom Hole Assembly (BHA) in a manner allowing for selective action at a remote location to cause the connector to disconnect the coiled tubing from the BHA.
Coiled tubing is a form of non-rigid hollow pipe designed for use in well bores to transmit mechanical torque and tension from a surface location to a BHA or other downhole entity, and to convey hydraulic fluid at pressure along the hollow interior of the tubing. At the same time (and unlike a conventional rigid drillstring), coiled tubing has sufficient flexibility to allow a substantial length of tubing to be stored on a reel in the manner of a hose. (This gives rise to the term xe2x80x9ccoiledxe2x80x9d; in normal use, xe2x80x9ccoiledxe2x80x9d tubing is de-coiled and is more or less straight, at least when in a wellbore).
With the continued and increasing use of coiled tubing for drilling, milling and workover applications in oilfield well-bores there is a need for more reliable and robust equipment which can be attached to the end of coiled tubing depending on the application and the work which is to be performed in the well-bore. Such equipment and tools are generally termed the xe2x80x9cBottom Hole Assemblyxe2x80x9d or xe2x80x9cBHAxe2x80x9d. On the majority of coiled tubing jobs, irrespective of application or equipment being used, there is the potential for the BHA to become stuck in the well-bore. In order to help alleviate the problems this can cause, certain xe2x80x9cemergency releasexe2x80x9d tools are available which can be used along with the BHA. These emergency release tools or xe2x80x9cdisconnectsxe2x80x9d are widely available from many suppliers and are fairly generic in design and method of activation. This familiarity and common design has the advantage that people are familiar in the way they operate and perform so eliminating potential problems that might arise from unfamiliarity with different methods of operation.
Disconnect tools are only utilised in an emergency situation if the BHA becomes stuck and the coiled tubing cannot be removed from the well-bore. The disconnect allows the coiled tubing to be safely parted at a known point within or adjacent the BHA, thus permitting the coiled tubing to be removed from the well-bore and a xe2x80x98fishingxe2x80x99 string to be used to remove the stuck tools separately. This fishing string would latch into a retrieval profile on the lower half of the disconnect tool with a specifically designed pulling tool.
In order to activate the disconnect tool, most known designs require a ball of specific size to be dropped from the surface through the coiled tubing until it reaches a ball seat within the disconnect. Once the ball has reached the disconnect, fluid flow is no longer possible through the coiled tubing. At this point the internal hydraulic pressure in the coiled tubing is increased to activate the release mechanism within the disconnect. This allows controlled separation of the upper and lower parts of the disconnect.
Conventional disconnect tools comprise two body members which are rotationally coupled together by a torque clutch mechanism in the form of corresponding castellations mounted on each coupling face of the body members. The conventional disconnect tools are longitudinally coupled by sprung outwardly loaded fingers which extend through the inner bore from one of the body members, over the castellated coupling, and latch onto a recess on the inner bore of the other body member.
The sprung outwardly loaded fingers are further pushed out, prior to disconnect, by a moveable piston which seats the fingers into the recess. When a ball is introduced, it lands on the piston, and moves the piston so that the fingers are no longer pushed into the recess, and which can move inwardly when the two body members are pulled apart, which disconnects the two body members.
According to the present invention there is provided a connector comprising first and second body members for connection to respective first and second entities to be connected together such that in use of the connector when the first and second body members are connected to the first and second entities respectively, the connector forms a substantially rigid connection between the first and second entities and is capable of transmitting mechanical forces therebetween, the first and second body members being mutually coupled by a first coupling arrangement on the first body member and a second coupling arrangement on the second body member, said first coupling arrangement comprising a plurality of discrete segments having respective segment surfaces which together define a formation engageable with a formation of the second coupling arrangement, and support means to support the segments in respective connection positions on the first body member in which the respective segment surfaces collectively form the first coupling arrangement, and release means selectively operable to disable the support means to cause or allow the segments to be displaced from their respective connection positions and disengage from the second coupling arrangement thereby mutually disconnecting the first and second body members of the connector.
Preferably, the first coupling arrangement is a first screw thread surface, the second coupling arrangement is a second screw thread surface, and the first and second screw thread surfaces are engaged when the first and second body members are connected.
Said segments may each be part-cylindrical. The segment surfaces collectively forming the first screw thread surface may be radially external surfaces of the segments, with the segments being displaced from their respective connection positions in respective directions each including a respective radially inward component. The support means may comprise a retainer member to retain each segment in a respective radially outwardly displaced position, and the release means may comprise retainer withdrawal means selectively operable to withdraw the retainer member from a segment-retaining position so as to allow the segments to move radially inwards and thereby disengage from the second screw thread surface. The retainer member may comprise wedges or slips insertable radially under each segment, and withdrawable by an axial sliding movement. The support means and the release means may be conjoined into a single component or assembly including a normally-open longitudinal through passage selectively closable to allow the application of fluid pressure sufficient to cause the axial sliding movement inducing withdrawal of the retainer member from the segments.
The connector may comprise a capture means to catch the support means after operation of the release means. The capture means is preferable mounted on the first body member.
The segments may be located, in use, within slots, where the slots may be formed on the outer circumference of the first body member. The segments and their respective slots may comprise differing circumferential extents. The segments and their respective slots may comprise a varied width along their longitudinal axis. The segments and their respective slots may comprise tapered side edges which taper in from the radially innermost surface of the segments and their respective slots to the radially outermost surface of the segments and their respective slots.
Typically, the connector further comprises a load bearing member which, in use of the connector, abuts an end of the segments.
The first entity may be coiled tubing and the second entity may be a bottom-hole assembly, the connector functioning as a selectively operable disconnect for separating the coiled tubing from the bottom-hole assembly.